Original title: Digital Holographic Speckle Pattern Interferometry in Structural Diagnostics of Paintings: Toward Displacement-Based Heritage Metrology
Vivi Tornari · September 2026
Paintings can develop hidden flaws like cracks and loose layers beneath their surfaces long before you see visible damage. Conservators need safe ways to find these defects without touching the artwork. Researchers review a non-contact technique called Digital Holographic Speckle PatternA grainy pattern created when laser light scatters off a rough surface, used here to track surface movement. InterferometryA technique that uses the interference patterns of light waves to measure tiny changes in distance or shape.. The system gently warms a painting with low-energy heat and watches it cool down. It uses laser light patterns called speckles to track tiny movements as the surface relaxes. Because the painting is built from stacked layers, damaged zones move differently than solid areas. The authors show that tracking these tiny surface shifts over time reveals hidden flaws, how defects spread, and the overall stability of the painting. The method combines raw visual light patterns with calculated movement maps. This lets experts track transient mechanical reactions, helping protect delicate painted heritage by measuring physical movement instead of just capturing surface photos.
Imagine pressing your palm against a thin rubber sheet stretched over a frame. If the sheet has a small bubble underneath, pressing near it makes the bubble rise differently than the rest of the sheet. Now imagine you gently heat the sheet with a hairdryer, then watch it cool. The bubble will expand and contract at a different rate than the surrounding area, creating a telltale pattern of motion. In this paper, the painting is the rubber sheet, the bubble is a hidden detachment between paint layers, and the laser measures how the surface moves as the painting cools after a gentle warm-up.
Paintings don't just fade—they quietly fall apart from the inside. Detachments and cracks form beneath the surface long before they reach the visible paint layer. This method catches those hidden defects early, non-invasively, so conservators can intervene before irreversible damage occurs. It shifts diagnostics from looking at static images to measuring how a painting physically responds to its environment.
The abstract does not specify quantitative detection limits, such as minimum defect size or depth resolvable. It notes that DHSPI requires strict boundary conditions and controlled thermal excitation, which may limit applicability to large-format or irregularly shaped surfaces. The review does not provide experimental validation on actual paintings, only methodological evolution. Multimodal integration and AI-assisted interpretation are discussed only as future directions, not demonstrated results.
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Digital Holographic Speckle Pattern Interferometry in Structural Diagnostics of Paintings: Toward Displacement-Based Heritage Metrology — Vivi Tornari — Heritage — doi:10.3390/heritage9100379
Abstract licence: CC BY
Explanation generated by Synthesis from the abstract — it is not the original paper.